package com.yxx.queue;

import java.util.Scanner;

public class CircleArrayQueueDemo {

    public static void main(String[] args) {
        System.out.println("测试数组模拟环形队列的案例~");
        CircleArrayQueue queue = new CircleArrayQueue(4);
        char key=' '; //接受用户输入
        Scanner scanner = new Scanner(System.in);
        Boolean loop=true;
        while (loop){
            System.out.println("s(show):显示队列");
            System.out.println("e(exit):退出");
            System.out.println("a(add):添加数据到队列");
            System.out.println("g(get):取出队列数据");
            System.out.println("h(head):查看队列头的数据");
            key=scanner.next().charAt(0);
            switch (key){
                case 's':
                    queue.listQueue();
                    break;
                case 'a':
                    System.out.println("输入一个数：");
                    int value=scanner.nextInt();
                    queue.addQueue(value);
                    break;
                case 'g':
                    try {
                        int res = queue.getQueue();
                        System.out.printf("取出的数据是：%d\n",res);
                    }catch (Exception e){
                        System.out.println(e.getMessage());
                    }
                    break;
                case 'h':
                    try {
                        int res = queue.headQueue();
                        System.out.printf("头部数据为：%d\n",res);
                    }catch (Exception e){
                        System.out.println(e.getMessage());
                    }
                    break;
                case 'e':
                    scanner.close();
                    loop=false;
                    break;
                default:
                    break;

            }
        }
        System.out.println("程序退出！");
    }
}

class CircleArrayQueue {
    private int maxSize;//表示数组的最大容量
    /**
     * front含义做了一个调整：front就指向队列的第一个元素，也就是说arr[front]就是队列的第一个元素
     * front的初始值=0
     */
    private int front; //队列头
    /**
     * rear 变量的含义做一个调整：rear指向队列的最后一个元素的后一个位置，因为希望空出一个空间作为约定
     * rear的初始值=0
     */
    private int rear; //队列尾
    private int[] arr; //该数据用于存放数据，模拟队列

    public CircleArrayQueue(int arrMaxSize) {
        maxSize = arrMaxSize;
        arr = new int[maxSize];
        rear=0;
        front=0;
    }

    //判断队列是否满
    public boolean isFull() {
        return (rear + 1) % maxSize == front;
    }

    //判断队列是否为空
    public boolean isEmpty() {
        return rear == front;
    }

    //入队
    public void addQueue(int n) {
        //判断队列是否满
        if (isFull()) {
            System.out.println("sorry,the queue is full!");
            return;
        }
        //直接将数据加入
        arr[rear] = n;
        //将rear后移，这里必须考虑取模
        rear = (rear + 1) % maxSize;
    }

    //出队
    public int getQueue() {
        //判断队列是否为空
        if (isEmpty()) {
            throw new RuntimeException("the queue is empty!");
        }
        //这里需要分析出front是指向队列的第一个元素
        //1.先把front 对应的值保留到一个临时变量中
        //2.将front后移，考虑取模
        //3.将临时保存的变量返回
        int value = arr[front];
        front = (front + 1) % maxSize;
        return value;
    }

    //求出当前队列的有效数据个数
    public int size() {
        return (rear + maxSize - front) % maxSize;
    }

    //展示队列的所有数据
    public void listQueue() {
        if (isEmpty()) {
            System.out.println("the queue is empty");
            return;
        }
        System.out.println("the queue is:");
        for (int i = front; i < front + size(); i++) {
            System.out.printf("arr[%d]=%d\n", i % maxSize, arr[i % maxSize]);
        }
    }
    //展示队列头的数据
    public int headQueue(){
        if(isEmpty()){
            throw new RuntimeException("he queue is empty");
        }
        return arr[front];
    }

}
